Kaposi's sarcoma-associated herpesvirus (KSHV) is a new human herpesvirus (HHV8). Kaposi's sarcoma (KS) is the most common neoplasm occurring in persons with acquired immunodeficiency syndrome (AIDS). Approximately 15-20% of AIDS patients develop this neoplasm which rarely occurs in immunocompetent individuals 13, 14!. Epidemiologic evidence suggests that AIDS-associated KS (AIDS-KS) has an infectious etiology. Gay and bisexual AIDS patients are approximately twenty times more likely than hemophiliac AIDS patients to develop KS, and KS may be associated with specific sexual practices among gay men with AIDS 6, 15, 55, 83!. KS is uncommon among adult AIDS patients infected through heterosexual or parenteral HIV transmission, or among pediatric AIDS parenteral HIV transmission, or among pediatric AIDS patients infected through vertical HIV transmission 77!. Agents previously suspected of causing KS include cytomegalovirus, hepatitis B virus, human papillomavirus, Epstein-Barr virus, human herpesvirus 6, human immunodeficiency virus (HIV), and Mycoplasma penetrans 18, 23, 85, 91, 92!. Non-infectious environmental agents, such as nitrite inhalants, also have been proposed to play a role in KS tumorigenesis 33!. Extensive investigations, however, have not demonstrated an etiologic association between any of these agents and AIDS-KS 37, 44, 46, 90!.